The present invention relates to the treatment of hydrocarbon material with electromagnetic energy, and more particularly to a method and apparatus for recovering fractions from hydrocarbon material, facilitating the removal and cleansing of hydrocarbon fluids, insulating storage vessels, and cleaning storage vessels and pipelines.
The existing techniques of heating hydrocarbon material such as coal, lignite, peat, and kerogen or hydrocarbon fluids, i.e., those having a kinematic viscosity in the range of about 20 seconds Saybolt Universal to about 500,000 seconds Saybolt Universal at 100.degree. F., with conventional thermal conduction methods using steam, hot water, electric coils, plates, piping or tracers has only met with limited success due to the poor thermal conductivity of the hydrocarbon fluid. Further, even with extremely high temperature gradients and therefore energy expenditure these techniques still fail to achieve penetration into the fluid to any great distance when it is immobile. Hydrocarbon materials such as coal, oil shale and tar sands remain locked in geological formations for somewhat similar reasons, although some modest degree of success has been achieved in in situ removal by using fire floods, solvents, polymers, bacteria, water floods and steam floods, so-called "Huff and Puff."
The physical characteristics of oil sands oil, bitumen, oil shale, peat, and lignite, are quite different from those of conventional crude oil. The oil sands bitumen, oil shale, peat and lignite is much heavier and much more viscious than conventional crude oil, so that under reservoir conditions it is essentially immobile. In fact, the oil sands bitumen, oil shale, peat and lignite has essentially the consistency of tar and can be induced to flow only if the reservoir conditions are suitably altered, for instance by raising its temperature. Particularly in the last two decades, a variety of in situ recovery techniques have been studied, including such methods as the underground injection of steam, hot water and hot gas, ignition of the oil within the formation, and underground atomic explosions. A common goal of these techniques is to transfer heat to the oil formation to raise the temperature of the very viscious oil sufficiently above the in situ temperature of 10.degree. C. to 15.degree. C. so that the oil can flow and be swept from the host formation by a suitable pressurized gas or other pressurized fluid driving agent. Since the formation is quite impermeable and has very low thermal conductivity, heat transfer by conduction and convection, as in the foregoing methods, is a very slow process. Moreover, control of the movement of the injected heating fluid within the formation is difficult so that a major unsolved problem of in situ technology is that of directing the fluid to the region which is to be heated, this region being generally the volume of the formation between a system of injection and production wells.
U.S. Pat. Re. No. 31,241, reissued on May 17, 1983, discloses a method and apparatus for controlling the fluency of hydrocarbon fluids by using electromagnetic energy. In accordance with the method, hydrocarbon fluid present in a geological substrate or container is heated by electromagnetic energy in the frequency range of from about 300 megahertz to about 300 gigahertz to release the hydrocarbon fluid by increasing its fluency. The released hydrocarbon fluid is then removed. A heating system for an oil burner and an apparatus for increasing the fluency by heating a contained hydrocarbon fluid is also disclosed.
Heating with RF waves is generally an absorptive heating process which results from subjecting polar molecules to a high frequency electromagnetic field. As the polar molecules seek to align themselves with the alternating polarity of the electromagnetic field, work is done and heat is generated and absorbed. When RF energy is applied to hydrocarbons which are trapped in a geological formation, the polar molecules, i.e., the hydrocarbons and connate water, are heated selectively, while the non-polar molecules of the formation are virtually transparent to the RF energy and absorb very little of the energy supplied.
Unlike steam flooding, which depends on pressure to maintain temperature, RF waves can produce very high temperatures within hydrocarbon materials, such as kerogen in shale formations, without requiring pressure. So called "thief zones" which channel off steam from the desired payzone or seam with conventional techniques are of minor consequence in the case of RF waves since most of the energy will be absorbed in the payzone or seam to which it is directed.
There are numerous storage stock tanks, ship bunkers, pipelines, tankers and vessels which contain varying amounts of high viscosity oil which it is economically impractical to salvage. The high viscosity oil and sludge found at the bottom of oil tankers is presently removed by bulldozers which gain access to the hold of the tanker through an opening created in the hull. After removal of the sludge, the hull is resealed. This process is time consuming, expensive and wasteful.
The present invention represents an improvement over the method and apparatus disclosed in the aforementioned reissue patent for facilitating the removal of hydrocarbon fluids as well as providing a novel method and apparatus for recovering fractions from hydrocarbon materials, facilitating the removal and cleansing of hydrocarbon fluids, insulating storage vessels, and cleaning storage vessels and pipelines.